Water-degraded wood, chemical properties

During the early 1960 s a new class of chemicals containing one or more double bonds was used to treat wood vinyl type monomers that could be polymerized into the solid polymer by means of free radicals (2). This vinyl polymerization was an improvement over the condensation polymerization reaction because the free radical catalyst was neither acidic nor basic, nor does the reaction leave behind a reaction product that must be removed from the final composite, such as water. The acid and base catalysts used with the other treatments degrade the cellulose chain and cause brittleness of the composite. Vinyl polymers have a large range of properties from soft rubber to hard brittle solids depending upon the groups attached to the carbon-carbon backbone. 

Considerable efforts have been directed, during the last few years, to grafting various vinyl and acrylic monomers on cellulosic fibers or films in order to modify their properties in a predetermined way. It was shown that one can graft large amounts of vinyl-type monomers, such as acrylonitrile or acrylic esters on rayon, cotton, cellophane, paper, and wood, thus modifying the properties of the base material in many respects, and improving, particularly, dimensional stability, water repellency, and resistance to thermal and chemical degradation. 

Decrystallization. The crystallinity of cellulose is an inherent property that is an important determinant of its mechanical properties, affinity for water, and accessibility to chemical reagents. Because cellulose comprises almost 50% of the wood, its crystallinity is a determinant of the behavior of the wood as well. Any disruption or change in the crystallinity of the cellulose will cause significant changes in properties and, thus by our definition, degradation. 

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